I've been testing this app and found it very interesting except lacking of:
=> Two columns in landscape mode. Yes, I know have been discussed here, but I would like a configurable column layout for landscape... and portrait. The only other app that supports multiple columns is QuickReader family of readers (basically the same reader with different menu), but it lacks any other feature and does not respect book formatting.
Why? Because you want to do fast reading, because sometimes columns are too wide to read even in portrait... I will give all my support to an app that will have that feature with the quality of Marvin...
=> Good Hyphenation. Currently the only app that does good hyphenation is CoolReader in Android or Linux (and for Spanish only with a special hyphenation file created by community). None of iOS does it well. Does Marvin know eBook language and hyphen it according to Language rules or does it in English?